Lord Williamson of Horton, proposer of the amendment (picture House of Lords)

My first reaction when I heard of the proposal in the House of Lords to amend the EU Bill (scroll down to column 281) so as to require a minimum turnout of 40 per cent before a referendum result was deemed valid was to be appalled. It is fine that big political decisions should be taken by the voters directly – whether or not to join the euro, whether or not to leave the EU – but rather ridiculous that smaller, more technical changes should be agreed in the same way. Are 40 per cent of the voters really going to turn out to decide whether or not the decision-making mechanism for sorting out the methods of operational cooperation between national customs agencies should be unanimity or qualified majority voting? That is not the methods, but how to decide about the methods. 4 per cent would be a good turnout, never mind 40 per cent. More likely there would be 4 votes, not even 4 per cent but 4 votes.

But the government insists that such technical changes should indeed be decided directly by the voters, in which case a 40 per cent threshold is a real threat. The point of a referendum is to approve the change, not to block it, so a referendum invalidated by a low turnout is a block on integration, a roadblock to reform.

Looking more closely at the issue, in preparation for writing about it, I find that there is more subtlety to it that a simple threshold. The proposal is that, if the turnout is low, the issue returns to parliament rather than being decided by the referendum that nobody wanted. The approval of both houses would be sufficient instead. No mention is made in the proposal of the result of a low turnout referendum, merely that it is disregarded, but politically that result would be very important.

One could understand that parliament might decide to sustain an overall Yes vote even if the turnout were low, if the issue at stake were of sufficient importance. It might be worth putting up with the embarrassment. It would be much less likely that parliament would overturn an overall No vote on a low turnout – the political cost would be much higher – even though parliament actually supported the Yes side (there would only have been a referendum in the first place if both houses had supported the proposed treaty change already).

In this light, the proposed 40 per cent threshold is not an obstacle but could, in certain circumstances, actually prove to be a springboard. Unlikely circumstances, but not impossible ones.

The more serious question underlying this is the role of referendums at all. The referendum on EU membership in 1975, the first in British history, was advisory: the final decision still rested with parliament, but it decided in the light of the definitive expression of public opinion on 5 June 1975. The second national referendum, held earlier this year on electoral reform, was different. It was itself decisive, leaving no role for parliament to take any further decisions after the vote had been held. This automatic effect was why the issue of a minimum turnout threshold acquired such importance when the bill creating the referendum was debated – could it be right to institute a far-reaching change to the political system on the strength of a small minority of the votes? It also lent a new significance to the conduct of the referendum campaigns themselves.

After a general election, it is possible that candidates who won seats by cheating can be removed from office by a special electoral court. Labour former minister Phil Woolas lost a court case and was removed from parliament after complaints about his 2010 general election campaign were upheld in court. After a referendum, if there is no further role for parliament, there can be no such opportunity for reflection. An automatic referendum is a referendum that can be stolen, whereas an advisory referendum that is won by underhand methods is open for further review. Reviewing some of the arguments made by the No campaign, and even some of those of the Yes side, makes me glad that the result was not close and that the notion that it was stolen did not take root.

The amendment was passed by 221 votes to 216, so it remains for the government to think what to do next. Does it go back to the House of Commons to get the amendment removed again, or does it accept the amendment as offering more flexibility without undermining the political rationale for the referendum idea in the first place?

I am less interested in the threshold as such as I am in the idea that referendums should be advisory and not automatically binding. For this reason, I hope that the government accepts the amendment that was passed in the House of Lords yesterday. It’s not what I thought I would think, but new facts have changed my mind.